1. Field of the Invention
The present invention relates to a radiant tube supporting apparatus used as a radiant heat source for a heat treatment furnace of heating or annealing facilities of a material to be heat-treated.
2. Description of the Related Art
A radiant tube is usually used as a radiant heat source for a heat treatment furnace of heating or annealing facilities for a material to be heat-treated. The radiant tube comprises a heat-resistant alloy steel tube, and is arranged in the furnace through the furnace wall. The tube has a gas burner in the interior thereof, and the furnace interior is radiant-heated by red-heating the tube through combustion of a gas by igniting the gas burner. When arranging the radiant tube in the furnace, a U-shape, W-shape or P-shape portion running through the furnace wall is secured to the furnace wall, and the portion in the furnace expands and contracts with this secured portion as a fulcrum under the effect of thermal expansion.
FIG. 5 illustrates a typical structure of a conventional W-shape radiant tube. The W-shape radiant tube 2 having a tip portion connected by a bend 3 after running through a furnace wall 1 of the furnace body is arranged in the furnace. A gas burner 11 is arranged inside the entry side at the inserting portion of the radiant tube 2, and a recuperator 12, inside the exit side.
A supporting member 13 is attached to the bend 3 at the tip of the radiant tube 2 on the furnace interior side and a bracket 14 bearing this supporting member 13 is secured by welding to the furnace wall 1' on the opposite side. The supporting member 13 is slidably supported on this bracket 14. Similar apparatuses are disclosed in Japanese Unexamined Patent Publications No. 8-278,001 and No. 8-278,003.
The conventional supporting apparatus of a radiant tube comprising the supporting member and the bracket supporting the same provided in the furnace as described above has a problem in that a long-time service results in an increased sliding resistance between the supporting member and the bracket under the effect of thermal expansion, heat deformation, chemical changes, surface deterioration and other causes, thus preventing smooth sliding. As a result, a galling or a breakage is caused at the bearing portion, or a serious stress is produced in the radiant tube, causing bending, deformation and breakage, and hence leading to a shorter service life. Maintenance is not therefore easy.
A rotating member may be provided in the furnace, or a rolling member may be arranged at the bearing portion as a supporting apparatus of the radiant tube. However, exposure to high temperature is always existent, and these conceivable measures cannot be a complete solution of the foregoing problem.
The present invention provides a supporting apparatus for a radiant tube, which can solve the above-mentioned problem. More particularly, the invention provides a supporting apparatus which alleviates sliding resistance upon thermal expansion and contraction of the radiant tube, and achieve this at a low cost.